1. Field of the Invention
This invention relates to a magnetic recording tape cassette, and more particularly to a magnetic recording tape cassette in which the magnetic recording tape can be held in the correct position relative to the magnetic head during recording and reproduction.
2. Description of the Prior Art
There has come into practical use a magnetic recording system such as a digital tape recording system in which sound information and/or video information are recorded as digital signals instead of analogue signals. Digital signals are superior to the analogue signals in that they are relatively insensitive to noise and have a high S/N ratio, whereby reproduction quality can be improved. When using the analogue signal, the frequency band may be on the order of 10 KHz. However, in the case of a digital audio tape recording system, a recording region covering a frequency band on the order of about 100 KHz is required.
In order to enlarge the usable frequency band, there is employed a helical rotary head recording system in which the magnetic head for recording and/or reproduction is rotated or a multitrack fixed head recording system in which an increased number of recording tracks are employed. In the case of the multitrack fixed head recording system, approximately ten tracks are required to effect recording having a frequency band on the order of 100 KHz since the maximum recording frequency for one track is limited to 10 to 15 KHz due to limitation in recording wavelength. Thus, 14 to 20 tracks are required for one way recording when dynamic range and error correction are taken into account. At present it has been proposed to use thirty-six tracks, eighteen tracks for recording each way. When this is applied to a Philips type compact cassette in which the tape width is only 3.81 mm, the tape width which can be allotted to each track is as small as 100 .mu.m. In the conventional analog magnetic recording systems, the relative position between the recording tape and the magnetic head is not so critical since the number of the tracks is four at the most and a relatively large tape width can be allotted to each track. However, in the digital audio tape recording system in which each track can be allotted only a very small tape width, the relative position between the recording tape and the magnetic head is very critical.
In the conventional magnetic recording tape cassette, the recording tape is guided by a pair of guide pins which are fixed to the cassette casing on opposite sides of the magnetic head receiving opening formed on the front face of the casing. Since the guide pins are fixed to the cassette casing by insert molding of plastic material, verticality of the guide pins varies due to various factors such as the structure of the molds, the molding condition of the cassette casing and the plastic material used for the molding. Thus, the position of the guide pins relative to the magnetic head varies from cassette to cassette and therefore the position of the tape relative to the magnetic head during running cannot be stabilized so that the magnetic head cannot precisely trace the same track during reproduction as during recording, whereby the reproduction output power is lowered and drop-out occurs frequently.